Subject: [PATCH] block layer: add partial mappings support to bio_map_user
For target mode we could end up with the case where we get very large
request from the initiator. The request could be so large that we
cannot transfer all the data in one operation. For example the
HBA's segment or max_sector limits might limit us to a 1 MB transfer.
To send a 5 MB command then we need to transfer the command chunk by chunk.
To do this, tgt core will map in as much data as possible into a bio,
send this off, then when that transfer is completed we send off another
request/bio. To be able to pack as much data into a bio as possible
we need bio_map_user to support partially mapped bios. The attached patch
just adds a new argument to the those functions and if set will not
return a failure if the bio is partially mapped.
Signed-off-by: Mike Christie <michaelc@xxxxxxxxxxx>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@xxxxxxxxxxxxx>
---
block/ll_rw_blk.c | 5 +++--
fs/bio.c | 11 +++++++----
include/linux/bio.h | 5 +++--
3 files changed, 13 insertions(+), 8 deletions(-)
97fbe8e42375284c82814b95cde3bc18c00721cd
diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c
index f9fc07e..65c56b6 100644
--- a/block/ll_rw_blk.c
+++ b/block/ll_rw_blk.c
@@ -2293,7 +2293,7 @@ int blk_rq_map_user(request_queue_t *q,
*/
uaddr = (unsigned long) ubuf;
if (!(uaddr & queue_dma_alignment(q)) && !(len & queue_dma_alignment(q)))
- bio = bio_map_user(q, NULL, uaddr, len, reading);
+ bio = bio_map_user(q, NULL, uaddr, len, reading, 0);
else
bio = bio_copy_user(q, uaddr, len, reading);
@@ -2345,7 +2345,8 @@ int blk_rq_map_user_iov(request_queue_t
/* we don't allow misaligned data like bio_map_user() does. If the
* user is using sg, they're expected to know the alignment constraints
* and respect them accordingly */
- bio = bio_map_user_iov(q, NULL, iov, iov_count, rq_data_dir(rq)== READ);
+ bio = bio_map_user_iov(q, NULL, iov, iov_count, rq_data_dir(rq)== READ,
+ 0);
if (IS_ERR(bio))
return PTR_ERR(bio);
diff --git a/fs/bio.c b/fs/bio.c
index 1f3bb50..fd1e419 100644
--- a/fs/bio.c
+++ b/fs/bio.c
@@ -719,19 +719,21 @@ static struct bio *__bio_map_user_iov(re
* @uaddr: start of user address
* @len: length in bytes
* @write_to_vm: bool indicating writing to pages or not
+ * @support_partial: support partial mappings
*
* Map the user space address into a bio suitable for io to a block
* device. Returns an error pointer in case of error.
*/
struct bio *bio_map_user(request_queue_t *q, struct block_device *bdev,
- unsigned long uaddr, unsigned int len, int write_to_vm)
+ unsigned long uaddr, unsigned int len, int write_to_vm,
+ int support_partial)
{
struct sg_iovec iov;
iov.iov_base = (void __user *)uaddr;
iov.iov_len = len;
- return bio_map_user_iov(q, bdev, &iov, 1, write_to_vm);
+ return bio_map_user_iov(q, bdev, &iov, 1, write_to_vm, support_partial);
}
/**
@@ -741,13 +743,14 @@ struct bio *bio_map_user(request_queue_t
* @iov: the iovec.
* @iov_count: number of elements in the iovec
* @write_to_vm: bool indicating writing to pages or not
+ * @support_partial: support partial mappings
*
* Map the user space address into a bio suitable for io to a block
* device. Returns an error pointer in case of error.
*/
struct bio *bio_map_user_iov(request_queue_t *q, struct block_device *bdev,
struct sg_iovec *iov, int iov_count,
- int write_to_vm)
+ int write_to_vm, int support_partial)
{
struct bio *bio;
int len = 0, i;
@@ -768,7 +771,7 @@ struct bio *bio_map_user_iov(request_que
for (i = 0; i < iov_count; i++)
len += iov[i].iov_len;
- if (bio->bi_size == len)
+ if (bio->bi_size == len || support_partial)
return bio;
/*
diff --git a/include/linux/bio.h b/include/linux/bio.h
index b60ffe3..fc0906c 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -295,12 +295,13 @@ extern int bio_add_page(struct bio *, st
extern int bio_add_pc_page(struct request_queue *, struct bio *, struct page *,
unsigned int, unsigned int);
extern int bio_get_nr_vecs(struct block_device *);
+extern int __bio_get_nr_vecs(struct request_queue *);
extern struct bio *bio_map_user(struct request_queue *, struct block_device *,
- unsigned long, unsigned int, int);
+ unsigned long, unsigned int, int, int);
struct sg_iovec;
extern struct bio *bio_map_user_iov(struct request_queue *,
struct block_device *,
- struct sg_iovec *, int, int);
+ struct sg_iovec *, int, int, int);
extern void bio_unmap_user(struct bio *);
extern struct bio *bio_map_kern(struct request_queue *, void *, unsigned int,
gfp_t);
--
1.1.3
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